U.S. patent number 4,421,323 [Application Number 06/413,041] was granted by the patent office on 1983-12-20 for oil well string member with static seal.
This patent grant is currently assigned to Greene, Tweed & Co., Inc.. Invention is credited to John A. Burke.
United States Patent |
4,421,323 |
Burke |
December 20, 1983 |
Oil well string member with static seal
Abstract
An oil well string member has a cylindrical outer periphery
having first and second cylindrical surfaces axially spaced and
connected by a tapered ramp. The surfaces are radially inwardly of
the outer periphery. The first surface has a smaller diameter than
the second surface. A seal assembly is provided along the first
surface and arranged to respond to fluid pressure for moving the
assembly across the ramp to the second surface to a sealing
position.
Inventors: |
Burke; John A. (Rocky River,
OH) |
Assignee: |
Greene, Tweed & Co., Inc.
(North Wales, PA)
|
Family
ID: |
23635567 |
Appl.
No.: |
06/413,041 |
Filed: |
August 30, 1982 |
Current U.S.
Class: |
277/336;
277/626 |
Current CPC
Class: |
E21B
23/08 (20130101); F16J 15/48 (20130101); F16F
9/36 (20130101); E21B 34/105 (20130101) |
Current International
Class: |
E21B
23/00 (20060101); E21B 34/10 (20060101); E21B
23/08 (20060101); E21B 34/00 (20060101); F16F
9/36 (20060101); F16J 15/46 (20060101); F16J
15/48 (20060101); F16J 015/06 (); E21B
019/10 () |
Field of
Search: |
;277/30,31,116.2,115,117-122,116.8,124,190,191,12,32 ;138/109
;285/140,141,146,147,148 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ward, Jr.; Robert S.
Attorney, Agent or Firm: Panitch, Schwarze, Jacobs &
Nadel
Claims
I claim:
1. Apparatus comprising a member having a cylindrical outer
periphery, said outer periphery having first and second cylindrical
surfaces axially spaced and connected by a tapered ramp, said
surfaces being radially inwardly of said periphery with said first
surface having a smaller diameter than said second surface, a seal
assembly along said first surface, an end face of said assembly
remote from said ramp being arranged to respond to fluid pressure
for moving the assembly across the ramp to the second surface, said
assembly being arranged to expand in a radially outward direction
as it moves across the ramp so that a central portion of its
periphery projects beyond the periphery of said member when said
assembly is disposed along said second surface.
2. Apparatus in accordance with claim 1 wherein said assembly
includes a first sealing element of resilient material at said end
face and having a peripheral sealing lip, said end face being
recessed, a second sealing element of polymeric material, said
second sealing element having a surface adapted to be moved
radially outwardly by contact with said first sealing element, and
a third sealing element of metal floating on a heel of said second
sealing element, said heel and said third element having mating
angled surfaces spaced from each other in the absence of pressure
and adapted to be in contact when said heel has been expanded
radially outwardly due to movement across the ramp.
3. Apparatus in accordance with claim 1 wherein said member is
hollow and slideably supports therein a hollow piston which forms a
flow passage through said member.
4. A high pressure seal assembly for installation with a loose fit
and subsequent expansion in situ comprising;
(a) a first annular sealing element of resilient material having a
peripheral sealing lip, one axial face of said sealing element
being intended to be exposed to high pressure and being recessed,
and an axial projection on the other axial face of said first
sealing element,
(b) a second sealing element of polymeric material, said second
sealing element having a lip adapted to be forced outward by said
first element, said projection being received by said second
element in a manner so that the projection may cause the second
element to move axially,
(c) a third sealing element of metal floating on a heel of said
second element, said heel and said third element having mating
angled surfaces spaced from each other in the absence of pressure
and adapted to be in contact when said heel has been expanded in a
radial direction into contact with said third element.
5. A seal assembly in accordance with claim 4 wherein the angled
surfaces on said heel and third element which are closer to said
projection being longer than the other of said mating surfaces.
6. A seal assembly in accordance with claim 4 wherein said first
seal element is made from an elastomer which resists H.sub.2 S,
said second sealing element being made from
polytetrafluoroethylene, and said third sealing element being made
from metal which is noncorrosive with respect to H.sub.2 S.
7. A seal assembly in accordance with claim 4 wherein the outer
diameter of said third element exceeds the outer diameter of said
second element by a distance corresponding to the radial length of
said space between the heel and said third element.
8. An oil or gas well string member having static seals on its
outer periphery and arranged so as not to be damaged during
downward passage through an arcuate portion of a well casing, said
member having first and second cylindrical surfaces axially spaced
and connected together by a tapered ramp, said surfaces being
radially inwardly of the periphery of said string member, said
first surface being below and having a smaller diameter than said
second surface, a seal assembly along said first surface, said seal
assembly being arranged to respond to fluid pressure from below for
moving the assembly upwardly across the ramp to the second surface,
said assembly being arranged to expand sufficiently so that a
central portion of its periphery will project sufficiently radially
outwardly for contact with a portion of a well when the assembly is
on said second surface, said assembly including a first annular
sealing element of resilient material resistant to H.sub.2 S, a
second sealing element above said first sealing element and in
contact therewith, said second sealing element being made from a
polymeric plastic material, the upper end of said second sealing
element being of reduced diameter and defined by conical surfaces
converging inwardly, and a third sealing element of metal resistant
to H.sub.2 S, said third sealing element surrounding said
converging surfaces and spaced therefrom, said third sealing
element having radially inwardly converging surfaces on its inner
periphery, and said converging surfaces of said third sealing
element being adapted to mate with said conical surfaces on said
second sealing element.
9. A string member in accordance with claim 8 including a port in
said string member between said static seals, a hollow piston
supported by said member with a reaction surface on the piston
exposed to said port so that fluid from said port can move the
piston downwardly and can move the static seals axially in opposite
directions, means on said member for causing said static seals to
expand as they move axially.
10. An oil or gas well string member having first and second
cylindrical surfaces axially spaced and connected together by a
tapered ramp, said surfaces being radially inwardly of the
periphery of said string member, said first surface having a
smaller diameter than said second surface, a seal assembly along
said first surface, said seal assembly being arranged to respond to
fluid pressure for moving the assembly as a unit from the first
surface across the ramp to the second surface, said assembly being
arranged to expand sufficiently in a radial direction so that a
central portion of its periphery will project sufficiently radially
outwardly for contact with a portion of a well when the assembly is
on said second surface, said assembly including a first annular
sealing element of resilient material resistant to H.sub.2 S, said
assembly including a second sealing element in contact with said
first sealing element and being made from a polymeric plastic
material, said assembly including a third sealing element
surrounding said second sealing element and being arranged to
prevent extrusion and cold flow of the second sealing element, said
string member being hollow so that oil or gas may flow
therethrough, and means on at least one end of said string member
for securing said string member to another string member.
Description
BACKGROUND OF THE INVENTION
After an oil or gas well has been drilled, it is necessary to
introduce into the well a valve string so that the oil or gas may
be removed in a controlled manner. A packer is attached to a wire
line and introduced into the well. The weight of mud plus a
pressure lock at the top of the well holds down the oil and gas.
When the packer is installed at the bottom of the well, it includes
a valve which is in a closed position. The wire line is retrieved
and attached to a series of valves which are then introduced into
the well. The first valve in the string is a sub-surface safety
valve which is held closed by springs and well pressure. The only
way to open that safety valve is to introduce a higher hydraulic
pressure to override the springs and override the forces of well
pressure. The safety valve must be closed when the well is
swabbed.
One problem in connection with oil and gas wells is the presence of
wet sour gas containing hydrogen sulfide (H.sub.2 S) and other
corrosive fluids. H.sub.2 S is a colorless gas which is extremely
dangerous if inhaled since the normal tolerance is two parts per
million. In addition, H.sub.2 S is extremely corrosive since it
forms sulfuric acid when combined with water. Hence, sealing is a
severe problem. When H.sub.2 S is encountered during drilling, the
normal procedure is to close the well permanently or burn it
off.
Another problem associated with off shore drilling is the provision
of a normally 20 foot radius in the well casing which must be
traversed by the valve string. When traversing the 20 foot radius,
seals on the periphery of the valve string can be damaged.
Another problem in connection with deep drilling is to provide
seals which can withstand the temperature and pressures involved.
For example, at a depth of 15,000 feet one frequently encounters
temperatures of 400.degree. F. and pressures of 15,000 psi.
The present invention is directed to a solution of the
above-mentioned sealing problems whereby a valve string may
traverse a 20 foot radius in the well, will provide for controlled
flow in hostile environments including H.sub.2 S, and has seals
reliable at temperatures of 400.degree. F. and pressures of 15,000
psi. The solution to the H.sub.2 S problem will enable all
previously closed wells to be activated.
SUMMARY OF THE INVENTION
The apparatus of the present invention includes a hollow member
having a cylindrical outer periphery. The periphery has first and
second cylindrical surfaces axially spaced and connected by a
tapered ramp. The surfaces are radially inwardly of the periphery
with the first surface having a smaller diameter than the second
surface. A seal assembly is provided along the first surface. An
end face of the assembly remote from the ramp is arranged to
respond to fluid pressure for moving the assembly across the ramp
to the second surface. The assembly is arranged to expand
sufficiently so that a central portion of its periphery projects
beyond the periphery of said member when said assembly is disposed
along said second surface.
It is an object of the present invention to provide apparatus which
will operate in the hostile environment of H.sub.2 S with well
pressures up to 22,500 psi and oil or gas temperatures to
400.degree. F. or higher.
It is an object of the present invention to provide an oil well
string member with seals which will not be damaged when traversing
a 20 foot radius in a well.
It is another object of the present invention to provide a novel
high pressure seal assembly.
Other objects and advantages will appear hereinafter.
For the purpose of illustrating the invention, there is shown in
the drawings a form which is presently preferred; it being
understood, however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
FIG. 1 is a vertical sectional view of a string member traversing
an arcuate section of a well casing.
FIG. 2 is a view similar to FIG. 1 but showing the string adjacent
the packer nipple at the bottom of the well.
FIG. 3 is an enlarged detailed view of the circled portion in FIG.
1.
FIG. 4 is an enlarged detailed view of the circled portion in FIG.
2.
DETAILED DESCRIPTION
Referring to the drawing, wherein like numerals indicate like
elements, there is shown in FIG. 1 a curved portion of a well
casing 10 adjacent the well head. The apparatus of the present
invention is designed so that it may traverse a curved portion of a
well casing having a radius of about 20 feet. The present invention
is also useful with well casings that do not have a curved portion.
The string member of the present invention is designated generally
as 12.
The string member 12 is adapted to be connected to other string
members by a ball joint received with the concavity 14 at the upper
end of the string member. The string member comprises a main body
16. A piston 18 is provided within the body 16. Piston 18 is hollow
and has an upwardly extending hollow extension 20 and a downwardly
extending hollow extension 21. Piston 18 and the extensions 20, 21
are hollow so that oil or gas may flow upwardly therethrough to
ground level.
Extension 20 is sealed to the main body 16 by seal 22. The piston
18 is provided with a seal 24 in contact with the inner periphery
of the main body 16. Seals 22 and 24 preferably include
anti-extrusion rings. A port 26 is provided in the main body 16 so
that fluid may be introduced to a reaction surface on the piston 18
and cause the extensions 20 and 21 to move downwardly when the
string member 12 is at the bottom of the well. Static seals 27 and
29 are provided on the outer periphery of the string member 12 on
opposite sides of the port 26.
When traveling down the well, seals 27, 29 are in the position
shown in FIG. 1. When hydraulic fluid under pressure is
communicated to port 26, static seals 27, 29 contain the hydraulic
fluid since the seals are on opposite sides of the port 26. The
seals 27, 29 are on a reduced diameter portion of body 16 and are
shifted axially in opposite directions to the positions shown in
FIG. 2. As the seals 27, 29 are shifted, they move along a ramp to
an enlarged diameter portion and expand into contact with a portion
of well packer nipple 25 shown in FIG. 2. Ramping of seals 27, 29
is similar to the ramping of seal assembly 36 described
hereinafter.
Radially inwardly of its periphery, the string member 12 has
axially disposed surfaces 30 and 34 on the body member 16. The
surfaces 30 and 34 are spaced from one another by a tapered ramp
32. The diameter of surface 34 is less than the diameter of surface
30 by a dimenson such as 0.1 inches. Each of the surfaces 30 and 34
has an axial length sufficient to accomodate a seal assembly
36.
The seal assembly 36, as shown more clearly in FIG. 3, is comprised
of a first seal element 38. The seal acts to shift the assembly 36
at the appropriate time. Further, element 38 is a molded homogenous
soft rubber member which performs two functions. The first function
is to act as a piston. The seal element 38 is designed so as to
survive the well environment particularly in the presence of sour
gas containing H.sub.2 S. The seal element 38 may be made from
various rubber compounds but is preferably made from a
fluoroelastomer characterized by regularly alternating
tetrafluoroethylene and propylene units. Such material has a long
term temperature resistance of 450.degree. F., is resistant to most
fluids and gases including sour gas, and has a high tensile
strength up to 3100 psi. One material which can be used for seal 38
is sold commercially under the trademark "Aflas".
The seal element 38 has a feathered lip 40 on its outer periphery
for line contact with the inner surface of the well casing 10. On
its inner surface, the seal element 38 is in planar contact with
surface 34. On its high pressure side, the seal element 38 has a
cavity 42 axially disposed with respect to an upwardly extending
projection 44 having a rounded nose.
The second seal element of the assembly 36 is designated 46. The
seal element 46 has an axially extended outer peripheral surface 48
spaced for substantial clearance from the inner surface of the well
casing 10. The seal element 46 has a pair of lips 50 and 52 which
embrace the projection 44. On its entire inner peripheral surface,
seal element 46 is in loose contact with surface 34.
The seal element 46 has a heel portion 54 defined by converging
surfaces 56 and 58 which converge radially inwardly and have an
included angle of about 90.degree.. Surface 58 is shorter in length
than surface 56. Seal element 46 is preferably made from
polytetrafluoroethylene having a 30% fiberglass load.
The third seal element of the assembly 36 is a zero clearance ring
62 made of a metal which is noncorrosive with respect to sour gas.
The ring 62 floats freely on the heel 54 and is spaced therefrom by
the gap 60. Ring 62 has a slight clearance gap 64 between its outer
periphery and the inner periphery of the well casing 10. Ring 62
has converging surfaces 66 and 68 on its inner periphery for mating
with the surfaces 56, 58 respectively when the heel 54 is expanded.
Surfaces 56, 58 cooperate with surfaces 66, 68 to prevent axial
separation of seal elements 46, 62 while traversing to the bottom
of the well. Ring 62 prevents cold flow of the second seal element
46. Due to the difference in lengths of the surfaces 58, 60 and 66,
68, the axial force of fluid pressure applied to the first seal
element 38 will exceed any radial force and thereby prevent
extrusion or cold flow of the second seal element 46.
The seal assembly 36 is designed so as to be responsive to well
pressure when the safety valve is opened by hydraulic pressure. The
seal assembly has been tested and has withstood differential
pressures up to 22,500 psi while being bubble tight so as to have
zero leakage. The seal assembly was found to be safe at 25,000 psi
for six cycles with no leakage.
The string member 12 is adapted to traverse curved portions of the
well casing as shown in FIG. 1. When in place at the bottom of the
well as shown in FIG. 2, hydraulic fluid is introduced downwardly
from ground level through packer nipple 25 to the port 26 to shift
the piston 18 downwardly and to cause seals 27, 29 to shift as
described above. When the piston 18 is shifted downwardly, it opens
the safety valve at the bottom of the well. The gas and/or oil
travels upwardly through the hollow string member 16, and other
string members attached to it to ground level. At the same time,
seal element 38 is exposed to well pressure. Due to the material
from which it is made, the seal element 38 can withstand exposure
to H.sub.2 S. In response to the well pressure on the end face of
seal element 38, the seal assembly 36 shifts from the portion shown
in FIG. 3 to the position shown in FIG. 4.
When shifting from the position shown in FIG. 3 to the position
shown in FIG. 4, the assembly 36 moves up the ramp 32, onto the
surface 30. In doing so, the seal element 38 is expanded as is
shown in FIG. 4, surface 48 of seal element 46 moving radially
outward 0.04 to 0.06 inches and contacting the inner surface of the
well packer nipple 25. Surface 48 constitutes the primary high
pressure seal. In addition, the heel 54 deformed radially outwardly
into contact with the third seal element 62 so that surface 56
contacts surface 66 and surface 58 contacts surface 68. Once
ramped, as shown in FIG. 4, the assembly 36 does not move and
cannot be reused. It is a long term seal for the life of the
well.
The present invention can be used in other environments in addition
to oil and gas wells. Thus, the present invention could be used in
high pressure vehicle suspension systems or high pressure shock
absorbers. The invention solves the problem of high pressures
sealing without requiring close tolerances since the seal assembly
can be installed with a loose fit and expanded in situ when exposed
to high pressure.
The present invention may be embodied in other specific forms
without departing from the spirit or essential attributes thereof
and, accordingly, reference should be made to the appended claims,
rather than to the foregoing specification, as indicating the scope
of the invention.
* * * * *